CVE-2025-21941 drm/amd/display: Fix null check for pipe_ctx->plane_state in resource_build_scaling_params

In the Linux kernel, the following vulnerability has been resolved: drm/amd/display: Fix null check for pipectx-planestate in resourcebuildscalingparams Null pointer dereference issue could occur when pipectx-planestate is null. The fix adds a check to ensure 'pipectx-planestate' is not null befo...